Verified by Rachel Mayfield, Supply Chain Analyst - June 2026
Torx (six-lobe) driver sizes from T6 to T55, with the point-to-point dimension of the lobe in millimetres and typical applications. Torx Size Chart Torx sizes follow ISO 10664, where the T-number is a designation, not a measurement - a T25 has a 4.43 mm point-to-point lobe. The six-lobe drive spreads load over more contact area than a hex or cross head, which is why it resists cam-out and is used widely in automotive and electronics assembly.
| Torx size |
Point-to-point (mm) |
Typical use |
| T6 |
1.75 |
Small electronics, laptop screws |
| T7 |
1.99 |
Phones, cameras |
| T8 |
2.31 |
Laptops, hard drives |
| T9 |
2.50 |
Electronics |
| T10 |
2.74 |
Electronics, small appliances |
| T15 |
3.27 |
Appliances, automotive trim |
| T20 |
3.86 |
Automotive interior, machinery covers |
| T25 |
4.43 |
Automotive, garden machinery |
| T27 |
4.99 |
Automotive engine, brackets |
| T30 |
5.52 |
Automotive suspension, machinery |
| T40 |
6.65 |
Automotive, heavy brackets |
| T45 |
7.82 |
Heavy machinery, structural |
| T50 |
8.83 |
Heavy machinery, suspension |
| T55 |
11.22 |
Construction plant, heavy structural |
How to identify a Torx size
If the bit isn't marked, measure the point-to-point width of the star recess with calipers and match it to the table - a 4.43 mm recess is a T25. Going one size too small cams out and rounds the lobes; one size too large won't enter. The most-used sizes in general repair are T20, T25, and T30, which cover most automotive interior and underbonnet fasteners.
Security Torx (Torx TR, also called pin-in Torx) has a pin in the centre of the recess and needs a driver with a matching hole - written as T10H, T20H and so on. A standard Torx bit won't seat in a security Torx screw. External Torx (E-Torx) is the inverse, a star-shaped socket that fits over an external lobed head, sized E4 to E24 and not interchangeable with the internal T-series.
Related standards
- ISO 10664 - Hexalobular internal driving feature for bolts and screws
- Torx and Torx Plus are trademarks of Acument Intellectual Properties
References
- ISO 10664 - Hexalobular internal driving feature